Before the recent discovery of copper-oxide based superconductors, the materials with the highest superconducting critical temperatures (T.sub.c) were Niobium- and Vanadium-based intermetallic compounds with the "A15" structure type. These are based on stoichiometry A.sub.3 B, with the earliest examples V.sub.3 Si (T.sub.c =17K) and Nb.sub.3 Sn (T.sub.c =18K) discovered in 1953. T.sub.c 's in the vicinity of 20K are obtained for Nb-based materials only, with the record high T.sub.c of 23K for Nb.sub.3 Ge obtainable in sputtered thin films only, not in bulk material. The highest known bulk T.sub.c is 20.7K for Nb.sub.3 Ga. The existence of these and many other Nb-based superconductors with lower T.sub.c 's have led to the general belief that intermetallic superconductors should include Nb in the chemical system for the best results.
The superconducting magnets currently in wide use in machines such as MRI scanners employ Nb based alloy wire, but preparation of bulk materials with very high T.sub.c 's in the A15 structure type has proven difficult. In view of this difficulty, alternative intermetallic superconducting materials with high T.sub.c 's would be of considerable interest. Although the T.sub.c 's of such intermetallic superconductors might be expected to be lower than those of the copper oxide based ceramic superconductors, the better processability and manufacturability of metals, along with the likelihood of good superconducting critical currents suggests possible advantages over ceramic materials for use at low temperatures.
Although the T.sub.c 's of prior art boride superconductors are low, less than 12K, it has been widely speculated that the low mass of boron might result in the presence of high frequency lattice vibrations, and consequently the possibility for relatively high T.sub.c 's. Recently, indications of superconductivity were discovered in a Y--Ni-boride composition. See C. Mazumdar et al., Solid State Communications, Vol. 87(5), pp. 413-416. A newly discovered Y--Ni-boride, an intermetallic composition, was formed by melting Y, Ni and B in nominal 1:4:1 atomic ratio in an arc furnace, and had T.sub.c (onset) of about 12K. However, superconductivity was not present at high levels in the samples.
In view of the great significance of intermetallic superconducting compositions, a new such composition would be of great interest, both scientifically and technologically. This application discloses such compositions.